In a liquid crystal display (LCD) device, a liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on receiving light from a light source, thereby displaying images and data. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light. Generally, a bottom-lighting type backlight module and/or an edge-lighting type backlight module are/is provided.
FIG. 1 represents a typical backlight module 10 including two prism sheets 1, a diffusion sheet 2, a light guide plate 3, a reflective sheet 4, a light source 5 and a light source cover 6. The prism sheets 1, the diffusion sheet 2, the light guide plate 3 and the reflective sheet 4 are set parallel, on top of each other, in that order. The light source 5 may be any of electroluminiscent lamp (EL), cold cathode fluorescence lamp (CCFL), and light emitting diode (LED). The light source 5 is disposed adjacent to one side of the light guide plate 3. The light guide plate 3 has an emitting surface 7 and a bottom surface 8 opposite to the emitting surface 7. Light emitted from the light source 5 enters the light guide plate 3. Some of the light emits from the bottom surface 8 and reflected by the reflective sheet 4. The reflected light and the rest of the light emit from the emitting surface 7 of the light guide plate 3. Finally, the light passes through the diffusion sheet 2 and the prism sheets 1. The diffusion sheet 2 is configured for uniformly diffusing the emitted light. The prism sheets 1 are configured for collimating the emitted light, thereby improving the brightness of light illumination.
Most of light that passes through the light guide plate 3, the reflective sheet 4, the diffusion sheet 2, and the prism sheets 1, rays gets absorbed by the above optical elements 1, 2, 3, and 4. Thus, the backlight module has low brightness due to a lower light energy utilization rate thereof.
What is needed, therefore, is a light guide plate and a backlight module using the same which can improve their optical brightness.